Hydraulic clutch



Feb. 13, 1951 E. w. SMITH HYDRAULIC CLUTCH Filed May 11, 1948 FIG.4

FREQUENCY FlG..l

FIG. 2

FIG. 3

IN VEN TOR. 501mm? M 57/76 BY Am 3 ly in Figure 2, in which the coupling unit 4 controls the amount of thrust which is transmitted. In Figure 2 the two mass vibrating system which produces the resonance is indicated by ments to which the spring I is attached. Resonance may be established for such a mass unit by the addition of the compensating mass 6, which then establishes a resonant system in which the two masses 3 and t are coupled'by an elastic element 1. This itself is usual practice and does not per se form a part of the present invention. The coupling unit 4, which is shown more in detail in Figure 3 comprises a shaft or red 8, which is centrally located within the liquid filled cylinder 9. The rod 8' preferably passes through both ends of the cylinder extending beyond the end wall iii, of the cylinder as indicated'at II. Suitable liquid and fluid tight bearing elements i2 and is may be used at each end of the cylinder so that no liquid escapes from within the cylindrical walls. The cylinder is closed at both ends, at the forward end by a cap 14 which may be screwed into the wall of the. cylinder or attached in any other means, as, for instance, by a flange, welding, or other suitable manner. The shaft 8 has between its ends within the cylinder a piston 5 with a plurality of fine passages it through the piston to permit the desired volume of fiuid to flow back and forth between the chambers ii and I8 formed within the cylinder on either side of the piston wall. The passages 56 may be made in threaded members 59 which thread into the piston wall and are substantially flush with both faces. sages of larger cross'sectional area the thread members I9 may be removed and other threaded members used with the desired passage openings through them. The piston iii may be welded orfixed-in any suitable way to the shaft 8. The

' piston preferably has a smooth, round fit with the cylinder wall, or such a fit that no fluid or liquid will escape around the piston to the wall edges. Any form of piston may be used and the piston may be provided with suitable piston rings if this proves desirable.

It is preferable, but not necessary in all cases, to carry the shaft 8 through the entire cylinder. By carrying the shaft 3 through the entire cylinder it is possible to have symmetrical chainbers ll and i8 and also to provide a system in which the volumetric changes in the two chambers are proportional'to the linear amplitude.

The cylinder 9 may be provided at one end with a yoke 26]- to which the mass element 3 may be attached for proper vibration.

The operation of the system and the function of the various elements are described below.

Let us suppose for a moment that the system is at rest and the motor is thrown on the line, the eccentric being set at the desired operating stroke, and that the motor, while able to deliver any normal thrust requirement during the running condition, is nevertheless not able to deliver much more than this.

As soon as the motor starts to rotate it is loaded with thrust required to move the vibrating system at the same amplitude which it is not able to do and therefore the perforated When it is desired to use pas- I 4 piston starts to slide inside the cylinder allowing the oil 2| or other liquid used to pass slowly from one side of the piston to the other. Since the perforations offer some resistance to the passage of the liquid the net result is'that some thrust is transmitted to the vibrating system I, although at a lesser amplitude than that of the-piston. V q

Under the above conditions the motor, not being loaded beyond its full load capacity, gradually builds up in speed and at the same time delivers thrust pulsations of the same frequency but at lesser amplitude to the vibrating system. This process'continues until the speed of vibration of the vibrating system reaches its resonant value which is assumed to coincide with the maximum speed of the motor under full load. When this condition is reached, as has been seen from Figure 1, the thrust requirement drops to a minimum which is compatible with what the motor can supply without overloading; At the same time, if the perforations in the piston have been so chosen that this amount of thrust is insuificient to drive any substantial amount of oil from one side of the piston to the other, there will be little or'no relative motion between the piston and the cylinder and the combination will act substantially as a rigid connection between the eccentric and the vibratory system I. V

In the design of the above transverse hydraulic clutch certain points are to be observed. It has been the inventors experience that such an oscillatory system as a rough average rule can be assumed to have a Q or amplification of about 10 to 12. Therefore, ifthe resonant system has such constants for its operating resonant frequency that the maximum force of the spring during vibration is, for instance, 5000 lbs. then the piston-cylinder system should be so designed that at least 500 lbs. of. alternating thrust are required to force any appreciable amount of oil from side of the piston to the other, at the frequency used. If this is done the amount of movement of the piston relative to the cylinder will be very little.

While the physical dimensions of the clutch are a matter of design taking into consideration the force to be transmitted and the available space limitations certain factors are of importance and should be taken care'of in the design.

First'it will be apparent that the larger the diameter of the piston can be consistent with the force to be transmitted the lower the pressure per square inch applied to the piston. This makes possible the use of larger holes in the piston and therefore more manageable ones. It also increases the necessity for extremely tight packin glands to prevent leakage of oil. I

Secondly it is desirable that equal motion of the piston in either direction produce equal volume changes in the oil on the two sides of the piston. Thus if the shaft carrying the piston does not extend through both chambers, the amount of motion required to transfer a given amount of oil through the perforations in the piston will vary with the direction of travel of the piston.

Thirdly, if the motion delivered to the clutch is not a pure sinusoid, as can readily be the case where the ratio of offset on the eccentric is not extremely small in relation to the length of the connecting rod, then the inequalities will be taken up in movement of the piston relative to the cylinder even at resonance with'a consequent unnecessary power loss and heating of the clutch to say nothing of probably loss of tight coupling at resonance.

Having now described my invention, I claim:

1. A vibrating system having a resonant vibratable element and a drive element for vibrating the resonant element, a coupling unit comprising an hydraulic cylinder having external means connected to one element of the system and a p ston operating therewithin forming fluid chambers on both faces of the piston, said piston having small communicating passages therebetween for the exchange of fluid between chambers and a rod connected to said piston at one end, and at the other end, to the other element of the system.

2. A vibrating system of the type described, comprising an hydraulic coupling unit having a housing forming a piston chamber, a piston positioned within the chamber and adapted to be reciprocated therein, a piston rod attached there to forming one end of the coupling unit, means attached to the housing forming the other end of the coupling unit, a non-resonant driving system connected to one end of the coupling unit and a resonant driven system connected to the other end of the coupling unit, means forming a communicating passage between the portions of the chamber separated by the piston and fluid means filling the chamber, said piston rod extending through the chamber and projecting at both ends thereof.

3. A vibrating system of the type described, comprising an hydraulic coupling unit having a housing forming a piston chamber, a piston positioned within the chamber and adapted to be reciprocated therein, a piston rod attached there- 3 to forming one end of the coupling unit, means attached to the housing forming the other end of the coupling unit, a non-resonant driving system connected to one end of the coupling unit and a resonant driven system connected to the other end of the coupling unit, means forming a. communicating passage between the portions of the chamber separated by the piston and fluid means filling the chamber.

4. A vibrating system of the type described, comprising an hydraulic coupling unit having a housing forming a piston chamber, a piston positioned within the chamber and adapted to be reciprocated therein, a piston rod attached thereto forming one end of the coupling unit, means attached to the housing forming the other end of the coupling unit, a non-resonant driving system connected to one end of the coupling unit and a resonant driven system connected to the other end of the coupling unit, said piston being provided with communicating passages from one face to the other comprising removable plug elements having holes of desired size therethrough, and fluid means filling th chamber and adapted to reciprocate through said passages from one face of the piston to the other.

5. In combination with a driven reciprocating vibrating system having a pronounced resonant frequency of operation, a mechanical driving ele.. ment, a non-resonant fluid coupling unit connected between the driving and driven element having fluid transfer means operative within the coupling unit for varying the ratio of motional amplitude between the driving and driven elements from ofi" resonance to on resonance of the system for operating the system at minimum thrust irrespective of frequency.

EDWARD W. SMITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,057,648 Lindhard Apr. 1, 1913 1,417,786 Walker May 30, 1922 FOREIGN PATENTS Number Country Date 577,445 France June 5, 1924 469,096 Germany Dec. 3,. 1928 

